Based on the one-dimensional salinity transport equation with constant diffusion coefficient, and separated water flow velocity into runoff and tidal current with the single-frequency in an idealized estuary, the simp...Based on the one-dimensional salinity transport equation with constant diffusion coefficient, and separated water flow velocity into runoff and tidal current with the single-frequency in an idealized estuary, the simplest unsteady analytical so- lution of salinity intrusion is deduced and the estimation formula of diffusion coefficient is obtained in this paper. The unsteady solution indicates that salinity process in estuaries results from the interaction of runoff and tidal current, and its amplitude is in direct proportion to the product of the velocity of runoff water and the amplitude of tidal flow velocity and in inverse proportion to the diffusion coefficient and the tidal angular frequency, and its phase lag tidal flow with 7/2 which reveals the basic features of the maximum salinity appearing after flood slack and the minimum salinity appearing before ebb slack under the effect of runoff （the advance or lag time is relative to the magnitude of runoff and tidal flow）. According to the measured flow velocity and salinity data, the salinity diffusion coefficient could be estimated. Finally, with the field data of observing sites on the deepwater navigation channel of the Yangtze Estuary, the diffusion coefficient is calculated and a comparative analysis of simulated and measured of salinity process is made. The results show that the solution can comprehensively reflects the basic characteristics and processes of salinity intrusion under the interaction of runoff and tidal flow in estuaries. The solution is not only suitable for theoretical research, but also convenient for estimating reasonable physical parameters and giving the initial condition in the salinity intrusion numerical simulation.展开更多
The longitudinal dispersion characteristics of tidal rivers areexperimentally investigated in a water channel. The longitudinal dispersion features and influentialfactors on pollutant in various stages of a tidal peri...The longitudinal dispersion characteristics of tidal rivers areexperimentally investigated in a water channel. The longitudinal dispersion features and influentialfactors on pollutant in various stages of a tidal period in natural rivers are studied; the valueranges and variation trends of the longitudinal dispersion coefficient are obtained by means ofconcentration measurement. The results can provide important parameters for establishing the waterquality mathematical models in tidal rivers.展开更多
Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyze the diffusion of suspended sediments and the change of tidal radial sand ridges in the n...Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyze the diffusion of suspended sediments and the change of tidal radial sand ridges in the northern part of the Changjiang River delta, the South Yellow Sea. The results showed that the diffusion of suspended sediments was controlled by the tide, net current, and submarine topography in this area. The distribution of suspended sediments had close relationship with the submarine topography. The old Huanghe River delta and the Changjiang River comprise the main sediment supply for the formation of radial sand ridges, whose evolution can be divided into three stages since the Huanghe River changed its course and flowed northward into the Bohai Sea.展开更多
Coral materials can replace concrete aggregates and achieve material self sufficiency for reducing the construction costs of island projects.This paper studies the effects of different mineral admixtures on the proper...Coral materials can replace concrete aggregates and achieve material self sufficiency for reducing the construction costs of island projects.This paper studies the effects of different mineral admixtures on the properties of coral aggregate concrete(CAC).The chloride concentration of CAC after different erosion times is measured using the potentiometric method,and the porosity of the CAC is ca lculated using thermogravimetric and drying methods.The chloride concentration of the CAC presents a two-phases dis tribution.The peak chloride concentration fol-lowed a power function,increasing with the erosion time.The chloride diffusion coefficient of CAC is 7.9%-37.5%larger than that of ordinary aggregate concrete,and the addition of 15% fly ash and 5%silica fume can significantly reduce the chloride diffusion coefficient,with a maximum reduction of 45.0%.The porosity obtained via the thermogravimetric and drying methods is well correlated.The porosity has a strong negative correlation with the compressive strength and a strong positive correlation with the chloride diffusion coefficient.展开更多
基金The research is partly supported by the Key Project of National Natural Science Foundation of China (Grant No.50339010)
文摘Based on the one-dimensional salinity transport equation with constant diffusion coefficient, and separated water flow velocity into runoff and tidal current with the single-frequency in an idealized estuary, the simplest unsteady analytical so- lution of salinity intrusion is deduced and the estimation formula of diffusion coefficient is obtained in this paper. The unsteady solution indicates that salinity process in estuaries results from the interaction of runoff and tidal current, and its amplitude is in direct proportion to the product of the velocity of runoff water and the amplitude of tidal flow velocity and in inverse proportion to the diffusion coefficient and the tidal angular frequency, and its phase lag tidal flow with 7/2 which reveals the basic features of the maximum salinity appearing after flood slack and the minimum salinity appearing before ebb slack under the effect of runoff （the advance or lag time is relative to the magnitude of runoff and tidal flow）. According to the measured flow velocity and salinity data, the salinity diffusion coefficient could be estimated. Finally, with the field data of observing sites on the deepwater navigation channel of the Yangtze Estuary, the diffusion coefficient is calculated and a comparative analysis of simulated and measured of salinity process is made. The results show that the solution can comprehensively reflects the basic characteristics and processes of salinity intrusion under the interaction of runoff and tidal flow in estuaries. The solution is not only suitable for theoretical research, but also convenient for estimating reasonable physical parameters and giving the initial condition in the salinity intrusion numerical simulation.
文摘The longitudinal dispersion characteristics of tidal rivers areexperimentally investigated in a water channel. The longitudinal dispersion features and influentialfactors on pollutant in various stages of a tidal period in natural rivers are studied; the valueranges and variation trends of the longitudinal dispersion coefficient are obtained by means ofconcentration measurement. The results can provide important parameters for establishing the waterquality mathematical models in tidal rivers.
文摘Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyze the diffusion of suspended sediments and the change of tidal radial sand ridges in the northern part of the Changjiang River delta, the South Yellow Sea. The results showed that the diffusion of suspended sediments was controlled by the tide, net current, and submarine topography in this area. The distribution of suspended sediments had close relationship with the submarine topography. The old Huanghe River delta and the Changjiang River comprise the main sediment supply for the formation of radial sand ridges, whose evolution can be divided into three stages since the Huanghe River changed its course and flowed northward into the Bohai Sea.
基金This study was supported by the National Natural Science Foundation of China(No.51590914).
文摘Coral materials can replace concrete aggregates and achieve material self sufficiency for reducing the construction costs of island projects.This paper studies the effects of different mineral admixtures on the properties of coral aggregate concrete(CAC).The chloride concentration of CAC after different erosion times is measured using the potentiometric method,and the porosity of the CAC is ca lculated using thermogravimetric and drying methods.The chloride concentration of the CAC presents a two-phases dis tribution.The peak chloride concentration fol-lowed a power function,increasing with the erosion time.The chloride diffusion coefficient of CAC is 7.9%-37.5%larger than that of ordinary aggregate concrete,and the addition of 15% fly ash and 5%silica fume can significantly reduce the chloride diffusion coefficient,with a maximum reduction of 45.0%.The porosity obtained via the thermogravimetric and drying methods is well correlated.The porosity has a strong negative correlation with the compressive strength and a strong positive correlation with the chloride diffusion coefficient.
